Suction box top



June 9, 1964 J. w. RIESE ETAL SUCTION BOX TOP 3 Sheets-Sheet 1 Filed NOV. 1, 1962 June 1964 J. w. RIESE ETAL 3,

SUCTION BOX TOP Filed Nov. 1, 1962 I5 Sheets-Sheet 2 June 9, 1964 J. w. RIESE ETAL 3,136,685

SUCTION BOX TOP Filed Nov. 1, 1962 3 Sheets-Sheet 3 United States Patent 3,136,685 SUCTION BOX TOP Jerome W. Riese, Neenah, and Karl E. Sager, Appleton, Wm, assignors to Kimberly-Clark Corporation, Neenah, Win, a corporation of Delaware Filed Nov. 1, 1962, Ser. No. 234,598 7 Claims. (Cl. 162-674) The invention relates to papermaking machines and, more particularly, to suction box structures for such machines.

As is Well known, a Fourdrinier type papermaking machine conventionally comprises a forming wire movably supported in the form of a loop and presenting a forming reach extending from a breast roll to a couch roll. Paper stock is deposited on the wire in the vicinity of the breast roll, and the formed web produced by drainage of water from the stock through the wire is removed from the wire in the vicinity of the couch roll. Various dewatering devices disposed beneath this reach of forming Wire commonly include suction boxes which present fiat perforate tops or covers to the bottom side of the wire. The suction boxes are exhausted so as to draw water through the wire and through the perforations in the fiat tops of the suction boxes from the web.

In the event that the openings in the suction box covers are not properly located with respect to each other, particularly if these openings are round holes, the suction effect on the web by the suction boxes in the cross direction of the machine, that is, transversely to the direction of travel of the wire and web, is not uniform and the web is not uniformly dewatered by the suction boxes; and it is an object of the present invention to provide an improved suction box cover having round openings which are so spaced and staggered with respect to each other that the web is substantially uniformly dewatered in the cross direction of the web and machine.

A preferred embodiment of suction box cover, according to the principles of our invention, is provided with a plurality (which may be designated in number by the letter N) of rows of openings, each row extending in the cross machine direction. The openings in each row are spaced center to center by a dimension or, and the openings of adjacent rows are spaced or staggered in the cross machine direction by a dimension b According to the invention, substantially uniform vacuum treatment of the web is provided by spacing and staggering'the openings with respect to each other in the cross machine direction, and so proportioning the values b and a to each other, by utilizing the formula b/a=n/N, where n is any integer whose only common factor with N is unity, n/N being an irreducible fraction.

The invention consists of the novel constructions, arrangements and devices to be hereinafter described and claimed for carrying out the above stated objects, and such other objects, as will be apparent from the following description of preferred forms of the invention, illustrated with reference to the accompanying drawings, wherein:

FIG. 1 is a perspective view illustrating the general arrangement of a papermaking machine in which our suction box cover may be used;

FIG. 2 is a plan view of a suction box having a cover made according to the invention and comprising a plurality of cover segments;

FIG. 3 is a sectional view taken on line 3-3 of FIG. 2;

FIG. 4 is a plan view of one of the box cover segments illustrated in FIG. 2;

FIGS. 5 and 6 are plan views of modified cover segments which may be utilized in lieu of the segment illustrated in FIG. 4; and

FIGS. 7 and 8 are plan views of hole patterns that may be used, according to the teachings of the invention.

Like characters of reference designate like parts in the several views.

Referring now to the drawings, the Fourdrinier papermaking machine illustrated in FIG. 1 may be seen to comprise an endless wire screen 10 disposed around end rolls 11 and 12 which may be trmed, respectively, breast and couch rolls. The upper reach of the wire 10 between the rolls 11 and 12 passes over table rolls 13 and suction boxes 14. A headbox 15 is disposed adjacent the roll 11 and is arranged to feed a slurry 16 of wood pulp and water on to the screen 10. One of the rolls 11 and 12 is driven so as to rapidly move the screen lil about the rolls 11 and 12. The slurry supported by the wire screen passes over the table rolls 13 and the suction boxes 14, and the water is drained from the slurry so as to form a paper web on the wire. The web is removed from the wire in the vicinity of the roll 12 and is passed to wet presses, drying rolls and calenders designated generally at 17. A partial vacuum is formed by each of the table rolls 13 adjacent its trailing side, and vacuum is applied to each of the suction boxes 14 to aid in drawing off a large portion of the water that drains from the stock on the wire 10 as the stock passes along with the wire from the roll 11 to the roll 12.

Each of the suction boxes 14 comprises a hollow base member 18 connected to one or more suction lines 19 and a cover 20 disposed on the top of the base member 18. Each of the suction lines 19 is connected to a vacuum source (not shown). The cover 20 is suitably fixed with respect to the base member 18 by means of a fixed clamp 21 on one side of the suction box and a removable clamp 22 on the other side of the suction box.

Each of the covers 20 comprises a plurality of cover segments 23 having end edges 24 and 25 that extend in the cross direction A of the machine and side edges 26 and 27 that extend diagonally with respect to both the cross direction and machine direction B (the direction in which the wire 10 travels). The cover 20 also comprises an end segment 28 having a diagonally extending edge 26 and an end segment 29 having a diagonally extending edge 27. The paper web formed by the slurry 16 passes over the suction box cover 20 as shown in FIG. 2 with the web edges 30 and 31 of the web being somewhat short of the ends of the segments 28 and 29.

The cover 20 of each suction box 14 is provided with a plurality of spaced openings 32 therethrough. The openings 32 in each segments 23 are disposed in a plurality of rows 33a, 33b, 33c, etc., that extend in the cross direction of the machine, parallel with the ends 24 and 25 of the segment, and the openings 32 are also disposed in a plurality of rows 34a, 34b, 340, etc., that extend parallel with the side edges 26 and 27 of the segment and diagonally with respect to the machine direction in which the Wire 18 moves.

The side edges 26 and 27 and the rows 34a, 34b, etc., in the particular cover segment illustrated in FIG. 4, extend at an angle of 61 /2 degrees with respect to the cross direction A of the machine and with respect to the end edges 24 and 25. The openings 32 in each of the rows 33a, 33b, etc., are a certain distance a apart along the rows, center to center, which is A; inch in the cover segment illustrated in FIG. 4. The openings 32 in the FIG. 4 form of cover segment are .869 inch apart, center to center, in the direction of rows 34a, 34b, etc., so that the distance b indicated in the figure,'which is the offset of the end openings in adjacent rows 33a, 3317, etc., is .869 inch times cosine 6l /2 degrees or .415 inch. The particular cover box segment illustrated in FIG. 4 has an N number of rows 33a, 33b, 330, etc., each of which extends in the cross direction, amountingto 19.

We have found that we obtain an optimum geometrical pattern of openings in a suction box cover for substantially uniform application of vacuum across the paper web, as is more fully explained hereinafter, if the following formula is followed in locating the openings: b/a=n/N where a and b are the spacings of the openings as above mentioned, N is the number of rows of openings that extend in the cross machine direction (rows 33a, 33b, etc. in the cover segment illustrated in FIG. 4) and n is any integer other than unity which does not have a common factor with N.

In the cover segment illustrated in FIG. 4, the values in this formula are as follows:

a inch .875 b do .415

It will be observed from FIG. 2 that the end segments 28 and 29 have the same patterning of openings as the segments 23 but that some of the diagonal rows are discontinued on their ends by the side edges of the end segments.

A modified suction cover segment 35 is illustrated in FIG. 5. This segment has ends 36 and 37 extending in the cross direction and side edges 38 and 39 extending at an angle of 61 /2 degrees with respect to the cross direction. Openings 40 are provided in the cover in diagonally extending rows 41a, 41b, etc., and in cross direction extending rows 42a, 42b, etc. The openings 40 in each of the rows 42a, 42b, etc., are spaced a distance a of .875 inch apart, and the openings 40 in the diagonally extending rows are spaced a distance of .856 inch apart. The dimension b, therefore, is .856 times cosine of 61 degrees or .408 inch. This suction box cover also complies with the formula b/a=n/N and, in this particular case, the quantities n and N are respectively: ":7 and N :15.

The suction box cover segment 43 illustrated in FIG. 6 also is made in accordance with the formula b/ a=n/ N discussed above. The segment 43 has end edges 44 and 45 and side edges 46 and 47. Openings 48 are provided in the cover segment, and these are disposed in rows 49a, 4%, etc., extending in the cross direction A and in diagonally extending rows 50a, 50b, etc. The side edges 46 and 47 in this embodiment extend at an angle of 60 degrees with respect to the cross direction A. The dimension a, which is the distance between adjacent openings 48 in the cross direction extending rows 49 is .793 inch, and the dimension b equals .846 inch (which is the distance between adjacent openings 48 in each of the diagonal rows 50a, 50b, etc.) multiplied by cosine 60 degrees or .423 inch. There are 15 rows 49a, 49b, etc., so, therefore, the integer n is 8.

The optimum geometrical patterning of openings in suction box covers prescribed by the relationship b/a=n/N discussed above results in treating each parallel machine direction section of the paper web on the Fourdrinier machine with the same total exposure to open area and hence to vacuum. Ideally, for most uniform treatment, no two openings shall fall at the same cross direction position, and utilizing the above mentioned formula, b/a=n/N gives this result. The simplified pattern of openings illustrated in FIG. 7 complies with this formula and illustrates the fact that, using the formula, no two openings fall at the same cross direction position. The FIG. 7 pattern includes openings 51 disposed in diagonally extending rows 52a, 52b, and in rows 53a, 53b, etc., that extend in the cross direction. Assuming that there are N rows of holes in the machine direction (8 rows are illustrated in FIG. 7), if the space between two adjacent openings in the first row 53a is divided into N equal spaces by (N-l) equally spaced dividing lines (54b, 54c, 54d, 54c, 54 54g, and 54h) extending in the machine direction B, maximum uniformity of application of suction is obtained by letting openings in each of the remaining cross direction rows 53b-53h, fall on one of the N-l dividing lines 54b54h.

Thus, with an opening 51 being located on a dividing line 54a, the first opening of the second rows 53b falls along the first (N -1) dividing line 54b, the first opening in the third cross direction row 53c falls on the second (N-l) dividing line 54c; the first opening in the fourth cross direction row 53d falls on the third dividing line 54d, etc. This patterning is repeated in the cross direction A across the cover or cover segment. Utilizing this simple arrangement, the above mentioned formula is satisfied as follows: b/a=l/N, where N =8 and b obviously is Mia.

FIG. 8 illustrates a patterning of openings 55 disposed in cross direction rows 56a, 56b, etc., and disposed on diagonally extending lines 57a, 57b, etc. There are openings 55a, 55b, 550, etc., in the first row 56a in the cross direction, and the openings on the diagonal line 57a are also disposed on the dividing lines 58b, 58c, 58d, and 53a between the openings 55a and 55b. Likewise the openings on the diagonal line 57b between the openings 55b and 550 are also disposed on equally spaced dividing lines 58g, 5311, 581', and 58j. In this case, the following formula applies: a/b= /s, the quantity N, which is the number of rows in the machine direction being 5, the integer n being 1, and the quantity b obviously being Via.

The integer n may also be 3, for instance, in the FIG. 8 example; and, in this case, the openings 59 on diagonals 60a, 60b, 60c, etc., will be provided in lieu of the openings 55 in the second, third, fourth and fifth rows 56b, 56c, 56d, and 56a. The integer n is the number of spaces formed by the equally spaced dividing lines that an opening in each succeeding cross row 56 is separated from an opening in the preceding row 56 so as to form the diagonals 66 which slant more with respect to machine direction B than do the diagonals 57. Changing the integer n from 1 to 3 thus causes an opening 59 in the cross row 56b to fall /5 of the distance between the openings 55a and 55b, namely on the dividing line 58d; the next opening 59 on the diagonal 60a is the same distance or 3 spaces in the cross direction, namely, on the dividing line 58g; and the other openings 59 in the cover are spaced the same distances or 3 spaces in the cross direction form preceding openings and on the diagonals 60a, 60b, etc. It will be apparent from comparing the patterning of the openings 59 and that for the openings 55 that both patterns result in only one opening on each of the dividing lines 58a, 58b, etc., in the machine direction B, while in one case, the integer n was 1 and in the other case the integer n was 3.

In the patterning illustrated in FIG. 8, the same result would be obtained, namely, an opening would fall on each of the dividing lines 58a, 58b, etc. if the first opening of the second row fell on either the dividing line 58c or the dividing line 5812, with the openings in the third, fourth, and fifth rows being spaced respectively the distance between two dividing lines or four dividing lines. In the first case, the quantity n in the formula would be 2 and in the second case, the quantity n would be 4.

Thus, in accordance with the invention, the optimum spacing of openings in a cover plate may be obtained by letting b/a=n/N, where n is an integer. The integer n should not have a common factor other than unity with N and n/N should be close but not equal to /2, as will be hereinafter explained.

The necessity for the restriction that there shall be no common factor between 11 and N may be demonstrated by setting N =6 and 11:2. Under these conditions, the openings on one diagonal would fall at /3, and equivalent to 1, equivalent to /3 and equivalent to Thus the positions /3, and 1 would be hit by two openings each of the openings on two diagonals while the positions /6, and /6 would be hit by no openings. This difficulty is caused by the fact that 11:2 and N 6, having the common factor of 2. On the other hand, if N were made equal to 7 (11 remaining equal to 2), an opening would fall on each dividing line from two diagonals giving more uniform application of vacuum to the web.

In this connection, it may be mentioned that the number of rows of openings in the machine direction (the quantity N in the formula) is preferably an odd number. In order that there may be quite uniform distribution and little ripple in the cross machine direction insofar as vacuum application is concerned, the number of rows and the quantity N preferably shall be 7 or greater, and such numbers as 17 or 19 are very desirable for this quantity.

The diameters of the openings should be large enough so that there is some overlap between the openings on adjacent dividing lines, the lines 58a, 58b, etc., for example, in FIG. 8. The opening diameters, therefore, ought to be greater than a/N, and; as a practical matter, in order to give good overlap, the opening diameters should be 2a/N or greater. In the cover segment illustrated in FIG. 5, the quantity 2a/N amounts to .117 inch, while the hole diameters are .625 inch, illustrating the fact that a/N is a preferable ratio as contrasted to 2a/N for the opening diameters in order that there may be substantial overlap between the openings on adjacent dividing lines and to provide maximum exposure to vacuum treatment without a substantial ripple or change in vacuum application in the cross direction.

It should also be mentioned that in order to obtain substantially uniform application of vacuum to the web and in order that there shall not be two openings having centers on the same dividing lines, such as the lines 58a, 58b, etc., of FIG. 8, each of the opening patterns should be used as units. In other words, an opening pattern satisfying the relation b/a=n/N should be used in its entirety in order to obtain substantially uniform application without the addition of the first rows of a similar pattern, although it will be understood that, if desired, two or more complete patterns of openings may be used in the same cover or cover segment.

In general, it is desired in a suction box cover or in a cover segment that a maximum open area be obtained consistent with substantial amounts of material remaining between adjacent openings. In order for these conditions to be satisfied, it has been determined that adjacent openings shall preferably have centers at the corners of equilateral triangles, or close to such corners. Thus, the angles of the side edges of the cover segments and the angles of the diagonals with respect to the ends of the cover or cover segments preferably should be 60 degrees or quite close to 60 degrees. It will be noted that these angles of the cover segments shown in FIGS. 4 and 5 are 61 /2 degrees and that the corresponding angle of the cover segment shown in FIG. 6 is 60 degrees. Also, in order that there shall be a maximum open area through the suction box or suction box cover, the integer n should be more than unity, and preferably the fraction 11/ N should be close to but not equal to /2. The ratio n/N would be exactly /2 if the openings are positioned at the corners of equilateral triangles, which is the best condition insofar as providing the maximum amounts of material between adjacent openings; however, if n/N equals /2 exactly, then N would equal 2n, and, therefore, n and N would have the common factor n which is not desirable as has been heretofore explained. Thus the fraction n/N should be close to /2 but not equal to /2. It may be noted that the fractions n/ N in the suction box cover segments illustrated in FIGS. 4 and 5 are respectively V and which are quite ideal from this standpoint.

To illustrate the reason for the preference that N should be an odd integer, cases in which N =19 and N may be compared, all of the ratios n/N being as close to /2 as possible. In connection with FIG. 4, the ratio n/N was as above explained which equals .474. A satisfactory ratio n/N using a denominator 19 would also be or .526, both .474 and .526 being substantially equally as close to /2 as the other. If N were made equal to 20, on the other hand, the n/N fractions closest to /2 would be 7 and or respectively .450 and .550. It will be noted that both of the latter decimals differ nearly twice as much from /2 as do 7 and just mentioned, thus illustrating the fact that the factor N should pref erably be an odd integer.

Thus, in accordance with the invention, in order to secure quite uniform application of suction to the web, the formula b/a=n/N should be followed in which n and N are integers whose only common factor is unity. The fraction n/N should preferably be close to /2, and the quantity N should preferably be an odd number. The diameters of the openings should preferably be at least 2a/N and still more preferably should be about lOa/N. Utilizing these principles, the resulting suction boxes and covers advantageously apply vacuum substantially uniformly to the web, being in this respect substantial improvements over prior covers that do not provide such uniform suction application.

We wish it to be understood that the invention is not to be limited to the specific constructions, arrangements and methods shown and described, except only insofar as the appended claims may be so limited, as it will be apparent to those skilled in the art that changes may be made without departing from the principles of the invention.

What is claimed is:

1. A suction box structure for dewatering a web on a traveling screen comprising a suction box with a generally flat cover adapted to contact the traveling screen, said cover having a plurality of drain openings therethrough which are arranged in rows that extend diagonally with respect to machine direction or the direction of screen movement and in rows that extend in the cross machine direction, said openings being arranged according to the formula b/a=n/N, where a is the distance between the centers of adjacent openings in the cross machine rows, b is the offset in the cross machine direction of the centers of adjacent openings in each diagonal row, N is the number of cross machine rows, and n is an integer whose only common factor with N is unity.

2. A suction box cover for papermaking machines of the type having a traveling web draining screen, said cover comprising a slab which is arranged to be mounted on a suction box to be in contact with the screen and to extend transversely of machine direction or the direction in which the screen travels, said slab being provided with drainage openings therethrough which are arranged in rows that extend in the cross machine direction and in rows that extend diagonally with respect to the machine direction, said openings being arranged according to the formula b/a=n/N, where a is the distance between the centers of adjacent openings in the cross machine rows, b is the offset in the cross machine direction of the centers of adjacent openings in each diagonal row, N is the number of cross machine rows, and n is an integer not having a common factor other than unity with N.

3. A suction box cover for papermaking machines as set forth in claim 2, each of said drainage openings having a diameter greater than 2a/N.

4. A suction box cover for papermaking machines as set forth in claim 2, said diagonal rows extending approximately at an angle of 60 degrees with respect to the cross machine direction.

5. A suction box cover for papermaking machines as set forth in claim 2, the quantity N, which is the number of cross machine rows, being 7 or greater and constituting an odd number.

6. A suction box cover for paperrnaking machines as set forth in claim 2, said diagonal rows extending approximately at an angle of 60 with respect to the cross machine direction and the ratio n/N being approximately equal to /2.

7. A suction box structure for dewatering a web on a traveling wire comprising a suction box having a generally fiat cover adapted to contact the traveling Wire, said cover comprising a plurality of cover segments laid side to side on the suction box, said segments having end edges that extend transversely of the machine and side edges that extend diagonally approximately at an angle of 60 degrees with respect to the machine direction or the direction in which the Wire travels, each of said segments being provided with Water drainage openings therethrough which are arranged in rows that extend in the cross machine direction and in diagonal rows that extend parallel with said side edges, all of said openings in each of said cover segments being arranged according to the formula b/a=n/N, where a is the distance between centers of adjacent openings in the cross machine rows, b is the offset in the cross direction of the centers of adjacent openings in each diagonal row, N is the number of cross direction rows and n is an integer not having a common factor other than unity with N, the diameter of each of said openings being greater than 2a/N and N being an odd number of 7 or more.

Milispaugh Dec. 1, 1931 Swauger May 26, 1936 

1. A SUCTION BOX STRUCTURE FOR DEWATERING A WEB ON A TRAVELING SCREEN COMPRISING A SUCTION BOX WITH A GENERALLY FLAT COVER ADAPTED TO CONTACT THE TRAVELING SCREEN, SID COVER HAVING A PLURALITY OF DRAIN OPENINGS THERETHROUGH WHICH ARE ARRANGED IN ROWS THAT EXTEND DIAGONALLY WITH RESPECT TO MACHINE DIRECTION OR THE DIRECTION OF SCREEN MOVEMENT AND IN ROWS THAT EXTNED IN THE CROSS MACHINE DIRECTION, SAID OPENINGS BEING ARANGED ACCORDING TO THE FORMULA B/A=N/N, WHERE A IS THE DISTANCE BETWEEN THE CENTERS OF ADJACENT OPENINGS IN THE CROSS MACHINE ROWS, B IS THE OFFSET IN THE CROSS MACHINE DIRECTION OF THE CENTERS OF ADJACENT OPENINGS IN EAHC DIAGONAL ROW, N IS THE NUMBER OF CROSS MACHINE ROWS, AND N IS NA INTEGER WHOSE ONLY COMMON FACTOR WITH N IS UNITY. 